Living organisms in any biome interact through a variety of relationships. Organisms compete for food, water, and other resources. Predators hunt their prey. Some organisms coexist in mutually beneficial relationships (symbiosis), while others harm organisms for their own benefit (parasitism). Still others benefit from a relationship that neither helps nor harms the other organism (commensalism).
Animals found in the Arctic tundra include herbivorous mammals (lemmings, voles, caribou, arctic hares, and squirrels), carnivorous mammals (arctic foxes, wolves, and polar bears), fish (cod, flatfish, salmon, and trout), insects (mosquitoes, flies, moths, grasshoppers, and blackflies), and birds (ravens, snow buntings, falcons, loons, sandpipers, terns, and gulls). Reptiles and amphibians are absent because of the extremely cold temperatures. While many of the mammals have adaptations that enable them to survive the long cold winters and to breed and raise young quickly during the short summers, most birds and some mammals migrate south during the winter
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ExplanatThe geometric or exponential growth of all populations is eventually curtailed by food availability, competition for other resources, predation, disease, or some other ecological factor. If growth is limited by resources such as food, the exponential growth of the population begins to slow as competition for those resources increases. The growth of the population eventually slows nearly to zero as the population reaches the carrying capacity (K) for the environment. The result is an S-shaped curve of population growth known as the logistic curve. It is determined by the equation As stated above, populations rarely grow smoothly up to the …(100 of 4579 words)
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In plant seeds, the photoreceptor phytochrome is responsible for the process termed photomorphogenesis<span>. This occurs when a seed initially situated in an environment of complete darkness is exposed to light. A brief exposure to electromagnetic radiation, particularly that whose wavelength is within the red and far-red lights, results in the activation of the photorecepter phytochrome within the seed. This in turn sends a signal through the signal transduction pathway into the nucleus, and triggers hundreds of genes responsible for growth and development</span>
